Carburetor



Patented Dec. 14, 1937 Y UNITED STATES PATENT OFFICE ApplicationFebruary 7, 1936, Serial No. 62,852 In Great Britain July 18, 1935 4Claims. (Cl. 261-116) This invention relates to carburetors forinterture of the air thus admitted may be from 35 to nal combustionengines, of the type in which the 70 C., for example, in the case ofgasoline of fuel is atomized with a primary supply of air at standardquality.

the head of a spraying nozzle and is then mixed 'Ihe cap 2| has acentral perforation 3l)` regis-V 5 with the main air supply passingaround the noztering With the bore of the fuel tube 22, the parts 5 zleinto a Venturi or choke tube. being secured together by means of aboss-3| on According to this invention, the spraying nozzle the bottomof the cap; this boss is shown as being comprises a central tube orpassage for the fuel counterbcred, coaxially with the perforation 30,surrounded by an air passage having at its upper to receive the upperend of the tube 22, which is end a perforated cap with a centraldivergent preferably soldered in place. 'Ihe exterior o'f the l0 cavity,the fuel being delivered axially intothis cap 2l is formed with arounded rim 32 which is cavity and the air being delivered'throughoblique shouldered down at 33 so as to tthe upper end holes in thedivergent walls of the cavity. of the outer tube'23, the cap 2I beingheld down Ihe invention is hereafter more fully described on the latterby the attachment of the inner tube l5 with reference to theaccompanying drawing, in 22; theirim 32 producesv a slight restrictionof the 15 whiehpassage through the choke tube I1.

Fig. l is a sectional elevation of the body or 'I'he choke tube I 'l hasapproximately the usual mixing chamber of a vertical carburetoraccordventuri-shaped or convergent-divergent interior,

,v ing to one embodiment of the invention. as indicated at 34, but thepassage area is con- I'2b Fig'. 2 is a similar view of a modification.trolled by the presence of steel balls 35 loosely en- 20 Fig. 3 is aplan View of the choke tube. v gaged in open-sided cells or flutings 36formed Fig. 4 illustrates the preferred method of makalong the interior.'I'he balls project inwardly of ing the choke tube. the choke tube,for'example to the extent of one- Referring to Fig. 1, the carburetorcomprises a quarter of their diameter, so as to restrict the pas- 2'5mixing chamber Ill having its lower portion II of Sage area at their ownlevel, as compared'with'the 25 frusto-conical shape, open to theatmosphere at circular or annular area of a normal choke tube the bottomand formed with a cross-bar I2 which 0f the Same dietlnetel-V Thelint/ings 36 :(See Figsuppgrts the spraying nozzle` I3,vv The upper part3) are preferably part-circular in cross-section,

I4 of the mixing chamber is 0f cylindrical shape', more thansemi-circular in extent, and of radius v 3() provided with means, suchas a flange V|5cf0r atslightly greater than the balls 35; their opensides, 30 tachment to the' throttle chamber I6 leading to towards theinteor of the choke tube. afford galos the engine. Inside' thecylindrical upper part I4 3l Slightly naITOWeF than the diameter of` thethere is mounted a choke tube I'I, resting upon a halls InOunteCl inthem- They extend longitudistep ls in the wan 0f the chamber, andretained nally down from the top of the choke tube to the Y by the angeI9 of the throttle chamber, Y level of the throat or narrowest portion38 of the 35 The spraying nozzle comprises a, Cap 2| secured interior,SO that in the nOIma] pOSilOli ShOWn in to the top of a central tube 22within an outer Fig. 1, With the balls resting at the bottom ofthetube'23, the latter being supported by a, polygonal Cells 0I` fllltlngs36, the area 0f the throat iS rebase 24 of which theshank 25 is screwedinto a StIiCted by the inwardly DIOjecting Surfacesof the 4o hole 26 inthe hollow cross bar I2 extending from halls; the thlOet 38 maycomprise, as' Seen in 40 one side to the other of the mixing chamber be-Fig- 1J a ShOIt Cylindrical DOItiOn betWeen the low the choke tube Il;the lower end of the mixing Convergent and divergent portions of thechoke. chamber is Shown as 0f greater Width, toi com- The top of thenozzle cap 2l provides a central pensate'for the restriction formed bythe crossdivergent CaVitY 39, 'in the form of a Shallow bar I2. Gasolineor 'other fuel is fed froma float inverted C0ne, COeXel With theDeI'fOIatiOn 30, 45 chamber (not shown) throughA a duct '21 in the thewalls of this conical cavity rbeing for example cross bar I2 to acentral bore v8 into; which the et an angle 0f 30 t0 the'hOIiZOhtal SOaS t0 lower end of the tube 22 is screwed or otherwise form a Sharp edgevat their junction With the rim secured so as to prevent leakage of fuelat this 32. Oblique hOleS 49, Di'efeiefhly three 0I' mOIe in point. Asecond ducty 29 eXtending in the opponumber, eVenlY SDaCeCl 'I'Ollnd theaXl'S, and Of a 50 site direction along the cross bar I2 admits air atdiameter Which may be IOIn 030 t0 i050 il'leh,A atmospheric pressure tothe space around the lowfor example, are formed-in the divergent Walls ier end of the fuel'tube 22, this air being warmed of the cavity 39,these holes connecting with the or heated if desired, for example lbycontact with tcp of an annular space or chamber 4I inside the exhaustmanifold of the engine; the tempera-` -the .tube 23 and concentric withthe fuel tube 65 lil 22; these holes 40 may also be inclined vat anangle of to the horizontal, and they are arranged in radial planes sothat their axes and that of the fuel tube 22 and perforation 30intersect at a point 42 within the cone 39.' Partitions or bales, forexample of helical form, may. be inserted in the annular chamber 4I, asindicated at 43.

The head of the nozzle I3 extends just above the level of the throat38,and the Vcircumferential rim 32 of the cap 2| projects about one or twomillimeters radially beyond the outer tube.

23; this rim 32 lies at a slightly' higher level than the restrictedarea provided by the projecting surfaces of the balls 35 in their normalposition. When more suction is applied by the opening of thethrottle,the increased flow fof air through the choke tube I'I tends to lift theballs 35 inside theirV n Y th1s blank is thenV bored out to form theconvergeht-divergent interior vofthe choke tube, as

cells 36 and carry them along to the upper and wider part of the choketube, thus removing the restriction from the throat and reducing itsproportional eiIect as the balls rise towards the final position shownin dotted lines at 35a in Fig. l. Y

But at the initial opening of the throttle from the idling position, thelifting of the balls first carries them to the level of the rim or bead32 at'the head of the nozzle I3, thereby producing a greaterrestriction, and only thereafter does the passage area become increased;the effect of this intial restriction is to provide a richer mixture atthe moment of opening` the throttle for acceleration after a period ofslow running, and thus to avoid the flat spot which is liable to causeengine stoppage under such conditions. y

In operation, the fuel issuing from the perforation 39 will be met bythe oblique streams of air drawn from theholes 40 by the injectoreffectv of the engine suction, these streams -breaking up the fuel intoa fine mist (as indicated at 44) which mixes with the main air supplypassing round the exterior of the nozzle I3; the atomizing air, drawnfrom the duct 29, will have passed through the interior of the'base 24into the annular space or chamber 4I between the two tubes 22 and 23, sothat this air (if sufciently heated) will have raised the fuel inthetube 22 to a temperature approaching or exceeding its initial boilingpoint, before it issues from the perforation 30, Vvaporization thereforetaking place immediately into the main air current.

VThe number and Vsize of the oblique air holes 40 may be varied; theseholes have a limiting effect upon the quantity of fuel passed at highspeeds, so that the fuel consumption remains approximately proportionalto the power developed. The divergent cavity 39 also acts to some extentas a basinrfor catching drops of fuel, the sharp edge of thercap abovethe rim 32 preventing the fuel from dribbling down the outside of thenozzle I3 at low speeds.

In an alternative construction, the Yair passage to the holes 40 may beformed by a pipe coil or spiral closely surrounding the fuel tube 22 andconnecting at its upper end with a perforated cap 2| screwed upon thefuel tube 22 and having a similar divergent cavity 39 with axial fueldelivery and oblique air holes. A

.The fuel may be Vsupplied to the nozzle in the form of an emulsion withairr by making use of Y the well-known system Yof compensating Vjets forthe same means as the atomizing air supplied to the passage 4I or by aseparate heater.

Fig. 2 shows a modified construction suitable for carburetors to befitted to relatively small engines; in this case the duct 29 forsupplying atmospheric air to the nozzle I3 is dispensed with, air beingadmitted to the annular passage or chamber 4I from the lower part of themixing chamber, by way of holes 45 formed in the outer Vtube 46. Thefuel tube 22 is securedat its lower end in the center of the base 24,which thus supports the complete spraying nozzle, allowing the latter tobe removed by unscrewing the base 24 from its hole in the cross bar I2.

The cells or flutings 36 in the choke tube I1 vcan conveniently beformed by drilling evenlyspaced oblique holes 4,1 into the body of acylindrical metal blank 48, as indicated in Fig. 4;

indicated by the chain-line circles 49---5Il` representing respectivelythe throat 38 and the top of the choke tube Il, thereby removing thewalls of the holes 4'I nearest to the axis for substantially the wholeof their axial length. The choke tube will then appear as shown in Fig.3, with theV open-sided cells or ilutings 36 each adapted to receive oneball. With a choke-tube having a 24 millimeter throat and an internaldiameter of 28 millimeters at the top, there may be employed nine ballseach 1/4 inch in diameter, fitted in cells or flutings formed bydrilling holes of fr inch diameter at an obliquity of 61/2 ydegrees tothe axis, corresponding to the divergent side of the choke, the pitchcircle of the balls varying by about 3 millimeters in diameter with anaxial movement of about 1/2 inch between their extreme positions. Whenfully raised, the balls willrbe retained by the connecting flange orfacing I9 to which the carburetor body is secured, so that they cannotslip out of place.

It will be understood that the invention is not limited to the use ofsteel balls as displaceable elements controlling the passage areathrough the choke tube II, and thatit may be applied to vcarburetors ofother types than that above described, for Yexample to carburetorshavingtlie axis of the choke tube I1 and spraying nozzle I3 inclined to thevertical; in cases Ywhere the axis approaches" the horizontal position,the gravity control of the displaceable elements may be supplemented orreplaced by spring or like control.

What I claim isz- 1. In a carburetor having a spraying nozzle mountedcoaxially within a choke, said nozzle comprising two concentric tubes,means for admitting fuel and atmospheric air respectively to the innerone of said tubes and to the annular space between said tubes, and acentrally perforated cap upon the upper ends of said tubes, a. rimaround said cap, said rim located above the .narrowest portion of saidchoke and projecting upper surface of said cap including adepressionaround the central perforation and a plurality of oblique holes spacedaround said central perforation, said holes communicating with saidannular space below said cap and converging upon the axis of saidcentral perforation at a point within said depression.

2. In a carburetor having a spraying nozzle mounted coaxially within achoke, said nozzle.

comprising two concentric tubes, a cap upon the upper ends of saidtubes, a rim around said cap,

said rim located above the narrowest portion of 7 5 said choke andprojecting radially beyond the outer one of said tubes, means foradmitting fuelV to the inner one of said tubes, and means for admittingair to the annular space between said tubes, said air-admitting meansbeing independent of the main air supply passing externally of saidnozzle, said cap having a perforation in line with said inner tube andalso a plurality of converging holes extending from said annular spaceto the upper surface of said cap, and the air admitted to said annularspace being discharged through said holes for mixture with fueldischarged through said perforation prior to meeting said main airsupply passing externally of said nozzle.

3. In a carburetor having a spraying nozzle mounted coaxially Within achoke through which the main air supply passes, said nozzle comprisingtwo concentric tubes, means for admitting fuel to the inner one of saidtubes, and means for admitting air at atmospheric pressure to theannular space between said tubes, and a cap surmounting said tubes, saidcap including a peripheral bead of diameter greater than the exteriordiameter of the outerone of said tubes, and the upper surface of saidcap being formed as a conical depression having a central perforationcommunicating With said inner tube and a plurality of oblique holesspaced round said perforation, said perforation being at the bottom ofsaid depression, and said holes communicating with said annular spaceand converging upon the axis of said perforationrat a point Within saiddepression. Y A Y 4. In a carburetor having a spraying nozzle mountedcoaxially within a choke through which the main air supply passes aroundsaid nozzle,

said nozzle comprising a central tube, a passage surrounding said tube,means for admitting fuel and atmospheric air to said tube and passage,and a cap surmounting said tube and passage, said cap having its uppersurface formed as a conical depression with a central perforationcommunicating with said tube and a plurality of oblique holescommunicating with said passage, and said cap including a peripheralbead located above the narroWest portion of said choke.

ARTHUR WILLIAM DAVID GLADWELL.

